1. Field of the invention
The present invention relates to a tube of non-woven material made from a heat-sealable non-woven and comprising a longitudinally extending connecting seal, more particularly a longitudinal seal obtained by ultrasonic sealing.
2. Description of the Prior Art
Such tubes of non-woven material for supporting a membrane for membrane filtrations are known in the art.
Known tubes of non-woven material comprising a connecting seal are inconvenient as a crack in the membrane may occur in the region of the provided longitudinal seal in case that the latter has not been applied in a careful and accurate manner. Actually a membrane in such a tube of non-woven material is subjected to a high internal pressure during a membrane filtration, which pressure may give rise to slight expansions of the membrane so that, especially in the regions where the fibers of the non-woven are sealed to each other, cracks may occur in said membranes so that they have to be discarded.
As already mentioned hereinbefore the application of a longitudinal seal has therefor to meet rather high critical demands as otherwise interruptions may occur in the apparatus having high production speeds.
It is an additional drawback of this known tube of non-woven material that the use of rather thin non-woven material causes the obtained tube to be relatively smooth which entails a difficult installment in an apparatus for membrane filtration in which such tubes of non-woven material comprising on their inner side a membrane are accommodated in a pressure-resistant support tube.
Other known tubes of non-woven material in which use is made of connecting strips obtained by employing an adhering means or glue have the drawback that a large strip of the non-woven becomes impermeable to liquids used in membrane filtrations.